Ball valve and seat assembly

ABSTRACT

A ball valve having an improved relationship between the ball and associated seat rings and an improved seat ring design. The ball is mounted for selective rotation and limited axial movement in a valve body passageway. Seat rings disposed on diametrically opposite sides of the ball about valve inlet and outlet openings each include a ball engaging surface having an arcuate contour. At a relaxed preassembly reference position, the radius of curvature of the ball engaging surface is greater than the radius of curvature of the ball. Frusto-conical disc springs interposed between each seat ring and an associated valve body shoulder additionally urge the seat rings into engagement with the ball. A reinforcing ring disposed at the forward end of each seat ring acts as a rigid bearing surface. Component sizing is such that in the assembled valve, the seat rings are slightly rotatably flexed in response to the engaging surfaces thereof engaging the ball such that the surfaces are distorted to have a mating relationship with the ball. At the same time, the disc springs are compressed while continuously urging the seat ring ball engaging surfaces into ball engagement.

This application is a continuation of application Ser. No. 348,718,filed 02/16/82 now U.S. Pat. No. 4,410,165.

BACKGROUND OF THE INVENTION

This invention relates to the valve art, and, more particularly, to ballvalves.

The invention is particularly applicable to a new and improved ballvalve and seat assembly for a valve of the type having a so-called"floating ball" and will be described with particular reference thereto.However, it will become readily apparent to those skilled in the artthat the invention is capable of broader applications and could beadapted for use in other types and styles of valves.

Ball valve constructions in commercial use typically employ annularseats or seat rings formed of a resilient and deformable plastic forsealing engagement with the ball. A pair of such seat rings arepositioned adjacent inlet and outlet openings. The ball itself ismounted for a slight amount of free movement or shifting axially of theseat when the ball is in a valve closed position under fluid pressureconditions. Such shifting causes the ball to act against and flex thedownstream seat ring to enhance its sealing engagement with the ball.The amount of such flexing varies in accordance with the fluid pressureinvolved.

The floating ball concept has been successfully used in manyarrangements and designs for small ball valves, and for lower pressureball valves. As fluid pressure increases and causes downstream shiftingof the ball, the ball is moved away from the upstream seat and all theforce is applied to the downstream seat. Since the seat comprises anannulus of a smaller area, seat stress is always greater than the fluidpressure. In addition, as the valve size itself increases, the hallforce increases as a function of the square of the seal diameter.However, typically it is impractical to increase the annular seat areaat the same rate. Therefore, in a large valve or at high pressure, theseat stress can reach levels that may crush ordinary plastic type seats.

An overall objective of ball valve seat designs is to obtain a valvewhich will seal at both low pressure and high pressure and that will notrequire an unreasonable amount of operating torque for rotating the ballmember. The floating ball type of concept is particularly advantageousin that it facilitates elimination of the more expensive trunnionmounted type of ball member as well as more complex pressure actuatedvalve seats.

Various forms and types of ball valve seat designs have heretofore beensuggested and employed in the industry, all with varying degrees ofsuccess. It has been found that the defects present in most prior ballvalve seat designs are such that the devices themselves are of limitedeconomic and practical value.

Prior ball valves employing an elementary seat have included a seatdesign typically comprised of annular resilient plastic seats merelycompacted between the ball member and opposed end fittings. The ballengaging surface of each seat includes a contour which matably engagesthe ball member periphery upon compacting assembly.

Elementary seat designs suffer from a number of inherent problems. In avalve closed position, the upstream pressure on the ball member forcesthe ball member into engagement with the downstream seat to seal thevalve in a virtual check valve type action. Since the pressure on theball member is substantially responsible for all the sealing force, atlow pressure or vacuum conditions, a low sealing force is present andresults in a leaking valve with leak paths between the seats and balland between the outer surfaces of the seats and supporting flanges orshoulders of the opposed end fittings. Elementary seat designs provideno compensation for wear or tolerance errors in the annular seats andthus associated leakage problems are compounded over a period of time.

At conditions where the upstream seat seals against the ball member, theadditional surface area of the upstream seat receiving load pressure isimparted against the downstream seat thereby increasing the load uponthe downstream seat resulting in increased downstream seat stress anddistortion. The force on the upstream seat to its outer diameter surfaceis translated through the ball member to the downstream seat. Suchincreased load area results in increased seat stress and thus causes anundesirable wear rate for the downstream seat. The problems of increasedseat stress and wear are particularly noticeable on the larger ballvalve sizes.

Also at conditions including upstream seat sealing against the ballmember at a valve closed position, a problem occurs with a "blowing-in"bulge on the upstream seat at the first opening of the valve. As thevalve is being opened, the upstream seat must momentarily span theopening or fluid passage extending through the ball and hold back fluidpressure. During this short period of time until the upstream seat sealis relieved by further opening of the valve, the portion of the seatspanning the fluid passage can deform into the passage under fluidpressure. With a small opening in the ball, the seat is quite rigid whenloaded as a beam in bending and can easily bridge the gap. As the valvesize and ball opening increase, the section modulus of the seat does notproportionately increase to retain the same stiffness. Thus, the seatmay deflect and deform further into the ball opening to form a bulge inthat sector of the seat ring.

As repetitive cycling occurs throughout the life of the valve, the bulgein the upstream seat becomes more pronounced and actually operates tocam a floating ball against the downstream seat as the ball member isrotated to the valve open position. The resulting camming action furtherstresses, even cutting, the downstream seat, and may ultimately distortand wear the seat into a non-operative condition. The bulge on the inletseat cams the ball off-center and holds it away from both seats whileclosed causing seat leakage in the closed position. It is particularlynoteworthy that the industry focused on the downstream seat assembly forpurposes of later improving ball valve operation to prevent valvefailures and problems caused by blowing-in bulges. In actuality,however, the upstream seat design was the cause of the problem. Theupstream seat permitted the blowing-in bulge and the resultant cammingaction which was reflected to the downstream seat.

Where soft plastic seats are employed, such as those made of Teflon,particular problems encountered with cold flow creep in the seat atnon-contained portions aggravate wear and undesirable seat deformation.

Blowing-in bulge aside, a sealing upstream seat has a generallyunsupported annular front face that can creep in toward the center ofthe valve when the valve is closed and under long duration static fluidpressure drop across the upstream seat. In the elementary seat designthe outside diameter of the seat ring is normally supported only by ashoulder in the valve body. The area of the seat and, therefore, theforce acting on it, increases as the square of the diameter. Since thesupporting shoulder is usually quite narrow and its area is more closelyrelated to the seat circumference, the supporting shoulder width onlyincreases in a linear fashion. This results in a narrow supportingshoulder which allows the seat to shear past it. Ultimately as the seatcreeps forward it can cave-in entirely or before that point it typicallycurls into the orifice of the ball such that when the valve is operated,the seat is torn. This problem also becomes more pronounced as the valvesize increases.

The down stream seat can also creep in toward the center of the valve byits generally unsupported annular front face. When the valve is in theclosed position, the seat may be displaced upstream by the ball memberpushing into it under pressure load.

Where large ball members are employed in large valves, the ball memberweight additionally contributes to the deformation and cold flowproblems. As the seats deform after a period of use the ball member maysag to the bottom of the valve, thereby providing a clearance at the topof the valve for a leak path.

An evolutionary step beyond the foregoing elementary seat design is thecontoured seat in which the ball engaging surface of the seat includes acontour different from that of the ball member outer periphery. Theobjective of this contoured design is to obtain a narrow band or linecontact between the seat and the ball which flexes slightly under loadsand retains contact with the ball at low pressure situations to give asealing stress at low pressure to minimize leakage between the ballmember and seat. However, in addition to retaining the other problemsassociated with the elementary seat design, the contoured seat suffersfrom the additional problems of extreme contact line distortion in highpressure conditions and rapid wear due to high seat stress since theentire sealing force was substantially borne by the contact line band.The extreme distortion and rapid wear further aggravated the otherproblems.

In order to overcome the particular wear problems of contoured seatdesigns, the flexible seat design, as is illustrated in U.S. Pat. No.2,945,666 evolved. The spring action of the flexible seat provided lowpressure contact, wear compensation, tolerance compensation and ball sagcompensation. However, this design suffers from the particular problemof providing improved operation for only a short period of time.

The seat is typically constructed of a plastic material which lacks anelastic memory and which deflects under load but does not return to itsoriginal shape when the load is removed. In addition, the flexible seatdesign employs less seat material at the contact line with the ball.After short periods of exposure to high pressure, the flexible seat willdistort to the shape of an elementary seat which is severely worn.

The problems of creep at non-contained portions of both upstream anddownstream seats, high downstream seat load due to an upstream seatseal, seat-to-shoulder leak paths, and seat blowing-in bulges all remainwith both the flexible seat design and the contoured seat design.

The industry next developed a ball valve seat design comprised of a seathaving a seat ring with a metal frusto-conical disc spring disposed inoperative engagement with the seat ring rear face. The disc springallows for improved compensation for seat ring wear, distortion andcreep as well as seat tolerance and ball sag, while providing an elasticsupport which effects a low pressure force bias. The disc springprovides seat elasticity not dependent on the elastic memory of theplastic seat material. However, while this is an improvement over thebefore-mentioned flexible seat design, the disc spring must,nevertheless, provide its elastic force while overcoming the elasticresistance of the plastic seat material.

A particular problem with this design is that the action of the springassures that the upstream seat seals against the ball member. Thus, theproblem of the elementary seat design having an effective load area onthe downstream seat substantially equal to the surface of the upstreamseat is not mitigated. The remaining unsolved problems include ablowing-in bulge, a weak seal at the seat-to-support shoulder contactarea and creep on the non-contained portions of both the upstream anddownstream seat rings. In addition, a problem with such design is thatthe disc spring need overcome the elasticity of the seat ring to effectthe low pressure force bias.

In order to meet the problems caused by an upstream or inlet sealingseat, the industry developed an upstream seat bypass arrangement such asis typically illustrated in U.S. Pat. No. 2,930,576. Various upstreamseat bypass methods and designs are employed including seat notches,grooves, holes, body orifices, and check valves. These variations areall for the purpose of communicating line pressure around the upstreamseat at the valve closed position for relieving the upstream seat ring,for reducing the load area by which the ball member imparts a load onthe downstream seat, and thus for reducing seat stress, creep and wearat the downstream seat ring. Also upstream seat blow-in and creep understatic pressure is circumvented. In addition, the necessary operatingtorque for opening and closing the valve is lessened.

Particular problems encountered with the upstream seat bypass designsinclude the need to provide dynamic seals due to bi-directional sealingof a ball-to-seat seal and a seat-to-body seal. A necessary consequenceof such complicated bi-directional sealing is reduced reliability ofsuch elaborate sealing. Problems of low pressure seat leakage,seat-to-shoulder leakage, compensation for tolerance, sag and wear arenot addressed.

Plugging of the bypass routes with contaminants in the valve systemfluid frequently occurs, especially where the valve is required tooperate in a dirty environment. Where a high viscosity fluid is employeda transient delay is often necessary before pressures equalize about theinlet seat thereby allowing the bypass routes to operate correctly. Inboth cases this seat design then assumes all the problems of anelementary seat design including a blowing-in bulge and cold flow creepat the non-contained portions of the seat rings.

A recent step in the evolution of ball valve designs comprises theprovision of a support ring opposite the disc spring to contain theplastic seat ring. The support ring operates to provide additional seatring support for bridging the ball passage at valve opening to minimizethe blowing-in bulge and the associated reflected distortion on thedownstream seat. Additionally, the support ring confines the seat tominimize cold flow creep distortion. However, those seat designs whichinclude disc springs and support rings are not without problems.Specifically, as with the before-mentioned disc spring and plastic seatdesign, the spring reserve of the seat-spring combination is determinedby the spring only which actually must overcome the plastic resistenceof the seat in order to move against the ball member and compensate forwear, tolerance and ball sag. The support ring in preventing the seatfrom caving in also hinders the seat from moving forward against theball. Thus, the seat is actually obstructed from moving against the ballmember by the support ring. While the support ring provides supportagainst seat creep and blow-in bulge it holds back the seat and springcombination from compensating for wear, tolerance, and ball sag. As thevalve is cycled and the seats are worn, the disc spring forces mustovercome both the elasticity of the seat ring and the rigid support ofthe support ring to effect seat to ball engagement.

It has, therefore, been desired to develop a ball valve and seatassembly for a floating ball type of valve which could be employed withhigher fluid system pressures while producing a longer life span thanhas heretofore been possible. Preferably, such a design would eliminatethe necessity for utilizing a trunnion mounted ball as is generallyconventional for ball valves employed in elevated fluid system pressureconditions. Trunnion mountings are not considered practical unless thevalve is quite large because such mountings substantially increase thesize, complexity and cost of the valves.

The present invention contemplates a new and improved construction whichovercomes all of the above referred to problems and others and providesa new and improved floating type ball valve and seat assembly whichfacilitate increased pressure capabilities and extend the effectivevalve life and wherein the seats may be formed from a wide variety ofmaterials to suit a wide range of operating conditions or parameters.

BRIEF DESCRIPTION OF THE INVENTION

Generally, the present invention contemplates a new and improved ballvalve and seat assembly wherein a seat ring with its own mechanicalelasticity is cooperatively disposed with an associated disc spring anda reinforcing ring to sealingly engage a ball member with asubstantially uniform stress distribution over a continuous seat ringengaging surface which faces the ball member. A pair of such assembliesare disposed on opposite sides of the ball member and are continuouslyurged toward the ball for maintaining it properly positioned in a valvebody and for providing valve sealing regardless of the fluid systempressure. The even distribution of stress over the seat ringsubstantially improves wear resistance in either high or low fluidsystem pressure conditions to prolong the valve life.

More specifically, the subject invention is particularly applicable touse in a valve of the type having a valve body with a centralpassageway, a ball member positioned in the passageway including a fluidflow opening and being mounted for selective rotation between valve openand closed positions to control fluid flow through the valve and furtherincluding a radius of curvature on an outer wall surface. A pair ofradially inward extending continuous shoulders are disposedcircumferentially of the passageway on opposite sides of and in a facingrelationship with the ball member. The passageway includes a pair ofcounterbores disposed on opposite sides of the ball member with each ofthe counterbores having a circumferentially continuous inner end wallfacing an associated one of the shoulders. A pair of composite seatmember assemblies are positioned axially in the passageway on oppositesides of the ball member for fluid sealing engagement with the ballmember. Each of the assemblies comprises a reinforcing ring, a springseat ring and a disc spring. The reinforcing ring includes a centralopening, a first surface facing an associated one of the shoulders, asecond surface abutting the end wall of the associated counterbore, anda third surface generally facing the ball member in a spacedrelationship therefrom. The spring seat ring is adapted forrotational-type flexure generally toward and away from the reinforcingring. The spring seat ring includes a central opening, a first surfacegenerally facing the associated one of the shoulders, a second surfaceabutting the reinforcing ring first surface, and a third surface facingthe ball member for sealingly engaging the ball member. This thirdsurface is contoured to include a radius of curvature greater than theradius of the ball member in an unstressed, unassembled condition. Thedisc spring has a generally frusto-conical configuration in anunstressed condition and is interposed between the spring seat ring andan associated one of the shoulders. The ball member and pair ofcomposite seat member assemblies are sized so that when assembled in thevalve body central passageway axially between the shoulders, the seatrings are flexed and stressed to have a radius of curvature at the thirdsurfaces thereof generally equivalent to the radius of the ball member.In this manner, substantially the entire extent of the seat ring thirdsurfaces sealingly engage the ball member. Simultaneously, the disksprings are stressed toward a flattened condition for continuouslyurging the seat ring third surfaces toward ball member sealingengagement.

In accordance with another aspect of the invention, the ball member andpair of composite seat members are sized so that when assembled axiallybetween the shoulders from a preassembly reference position, the seatrings and disc springs are flexed and stressed to have an axialdisplacement at the central openings thereof equal to an axial spacingof radially innermost ends of the seat ring second surfaces from theball valve member plus an axial displacement of the disc spring at anequicentric position to the axial spacing.

The principal object of the invention is the provision of a new andimproved ball valve and seat assembly which allow higher pressureratings and greater cycle life to be obtained from a floating ball typeof ball valve.

Another object of the present invention is the provision of such a ballvalve and seat assembly which will effect valve sealing even at very lowfluid system pressures.

Still another object of the present invention is the provision of a newand improved ball valve and seat assembly which permit the seat rings tosealingly engage the ball member over a surface of substantially equalstress distribution.

Still other objects and advantages of the invention will become apparentto those skilled in the art upon a reading and understanding of thefollowing specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangementsof parts, a preferred embodiment of which will be described in detail inthis specification and illustrated in the accompanying drawings whichform a part hereof and wherein:

FIG. 1 is a longitudinal cross-sectional view through a ball valve whichincorporates the preferred embodiment of the invention;

FIG. 2 is an enlarged cross-sectional view of the upstream seat assemblyjust prior to valve make-up and with the ball member deleted for ease ofillustration;

FIG. 3 is an enlarged cross-sectional view of the downstream seatassembly shown just prior to valve make-up and with the ball memberdeleted for ease of illustration;

FIG. 4 is a somewhat schematic view of the preferred seat assemblyconstruction shown just prior to valve make-up for showing variouscooperative relationships between the valve components;

FIG. 5 is a slightly enlarged view of a portion of the valve of FIG. 1showing the ball member in the valve open position under a no loadcondition.

FIG. 6 is an enlarged cross-sectional view of a portion of the upstreamseat assembly of the valve shown in FIG. 5;

FIG. 7 is an enlarged cross-sectional view of a portion of thedownstream seat assembly of the valve shown in FIG. 5;

FIG. 8 is a cross-sectional view similar to FIG. 5 but with the valve ina closed position under the influence of elevated fluid system pressuresand at such time that the seat assemblies have undergone considerablewear;

FIG. 9 is a enlarged cross-sectional view showing a portion of theupstream seat assembly of the valve shown in FIG. 8; and,

FIG. 10 is an enlarged cross-sectional view of a portion of thedownstream seat assembly of the valve shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein the showings are for purposes ofillustrating the preferred embodiment of the invention only and not forpurposes of limiting same, FIG. 1 shows a ball valve A having a pair ofopposed seat assemblies B disposed on opposite sides of a floating typespherical ball member C.

More particularly, and with reference to FIGS. 1 and 5, ball valve Aincludes a body or housing generally designated 10 having a main orcentral body section 12 and opposed end fittings 14, 16. Seat assembliesB and ball C are mounted within the main body section 12 and the ballmember is arranged for selective rotation by a stem and actuating handleassembly generally designated 18.

The details of all portions of the valve illustrated in FIGS. 1, 5 and8, except for the ball and seat ring assemblies, may be modified asdesired and/or necessary to accommodate different types or styles ofball valve constructions. In general, however, and for purposes ofdescribing the subject invention, the valve body includes a generallycylindrical central passageway or axially extending fluid flow opening20 which is only slightly larger in diameter than ball member C. Each ofend fittings 14, 16 is releasably connected to central body section 12by a plurality of longitudinally extending tie bolts generallydesignated 22 (FIG. 1). The end fittings are also provided with internalthreads 24, 26 or any other convenient means to accommodate connectingthe valve to an associated fluid system or piping.

The stem and actuating handle assembly 18 illustrated includes a stemmember 30 having a lower end 32 configured as shown for sliding receiptin a slot or groove 34 included in the upper end of ball C. Thisarrangement allows the ball to be rotated between valve open and closedpositions while at the same time permitting the ball to have somefreedom of movement for shifting axially in valve body passageway 20when the valve is in a closed position and fluid pressure is acting onthe ball.

Stem member 30 extends outwardly through an opening 36 in central bodysection 12. Suitable packing rings 38, 40 and 42 are positioned inopening 36 and sealingly engage the opening and stem member 30. Asshown, lower packing ring 42 rests upon an inwardly extending flange 44formed within opening 36. A split thrust washer 46 is positioned belowflange 44 and is clamped thereto by an outwardly extending shoulder orflange 48 formed at the base of stem member 30. The stem is held inposition by a packing gland 50 and a packing unit 52. As shown in FIG.1, tightening of packing nut 52 applies pressure to packing rings 38,40, 42 to assure a fluid-tight seal about the stem.

Although it is possible to actuate the valve stem by many differenttypes of actuators, including both manual or automatic, a handle member54 has been shown. This handle is releasably secured to stem member 30by a nut 56 which clamps the handle to the top of packing nut 52. Acooperating flat 58 is advantageously formed on the exterior of the stemfor association with a flat (not shown) in the handle opening forproperly positioning the handle on the stem. However, the position ofthe handle and, in turn, the position of ball member C are limited bydepending stop members 62, 64 carried by handle 54. These stop membersengage suitable surfaces on central body section 12 to provide fixedstops for the valve in the full open and full closed positions.

With continued reference to both FIGS. 1 and 5, the ball seatarrangement utilized in the subject invention includes a pair of seatring assemblies B disposed on opposite sides of ball member C. As shown,the seat ring assemblies are clampingly retained in position on oppositesides of the ball adjacent opposite ends of the main body sectionpassageway or opening 20. In the preferred embodiment hereunderdiscussion, the seat ring assemblies are located substantiallyequidistantly from and on diametrically opposite sides of the axis ofrotation of the ball member and include radially innermost centralopenings 66, 68. While the seat ring assemblies could be maintained inposition by many different or alternative arrangements, they are shownin the preferred embodiment as being located by shoulders 70, 72 definedby end faces 74, 76 of end fittings 14, 16, respectively. The inwardlimit of movement of the seat ring assemblies is defined by a pair ofshoulders or steps 78, 80 (FIG. 5) which are formed by the inner endwalls of counterbores extending inwardly of valve body passageway oropening 20. Still further, a seal is provided between central bodysection 12 and end fittings 14, 16 by means of O-rings 82, 84 which arereceived in second counterbores 86, 88, respectively. Each O-ring isdisposed about the outer circumference or outer peripheral surface of aportion of the associated seat ring assembly B.

The structural details of ball valve A described hereinabove are withreference to the preferred valve construction. It will be readilyapparent to those skilled in the art, however, that modifications mayreadily be made thereto to accommodate particular operational needsand/or requirements. Such changes are not deemed to affect the overallintent or scope of the present invention as will be described in detailhereinafter.

With reference to FIGS. 2, 3 and 4, description will be made of thespecific details of seat assemblies B. FIG. 2 shows a cross-sectionalview of the upstream seat assembly disposed adjacent end fitting 14prior to valve make-up. FIG. 3 shows a cross-sectional view of thedownstream seat assembly disposed adjacent end fitting 16 and isidentical to the upstream seat assembly. The ball member C has beendeleted for ease of understanding and appreciating the seat assemblyconstruction. FIG. 4 shows a somewhat schematic view of a seat assemblyjust prior to make-up where the ball member C has been included.

The seat assemblies are each preferably comprised of three components,i.e., reinforcing or support rings 100, 102, seat rings 104, 106 andfrusto-conical disc springs 108, 110, respectively. Reinforcing rings100, 102 have an annular configuration including a central opening andare constructed from a rigid material such as steel or other suitablemetal. In FIGS. 2 and 3, reinforcing rings 100, 102 are shown asincluding first circumferentially continuous surfaces or end faces 112,114 which face associated shoulders 70, 72 of end fittings 14, 16.Second continuous surfaces 116, 118 face and abut counterbore end wallsor steps 78, 80 of main body section passageway 20 to positivelyestablish a forwardmost or home position for the reinforcing rings. Athird continuous surface 120, 122 of each faces generally toward theball member (not shown), but is dimensioned to be spaced therefrom inorder to prevent any abutment or interference therewith and to inhibitdistortion and displacement of the associated seat ring between thereinforcing ring third surfaces 120, 122 and the ball member. The outercircumference or peripheral surfaces 124, 126 of rings 100, 102 areclosely disposed to the sidewall of passageway 20. Outer surfaces 124,126 and second surfaces 116, 118 may alternately include a flange orstep configured and dimensioned to engage shoulders 78, 80 to furtherextend portions of support rings 100, 102 axially inward of passageway20 where overall valve dimensions may so require. However, such anadditional flange is avoided in the preferred embodiment shown toobviate additional machining steps.

Referring still to FIGS. 2 and 3, it will be seen that seat rings 104,106 also comprise annular or ring-like members having central openings66, 68 therethrough which are smaller in size than the central openingsof the reinforcing rings 100, 102. The seat rings are adapted forflexure generally toward and away from the reinforcing rings 100, 102.Seat rings 104, 106 are configured to exert a spring-like mechanicalelasticity against the ball member. First surfaces 128, 130 generallyface the associated shoulders 70, 72 of end fittings 14, 16 and, inrelation to shoulders 70, 72, are inclined or tapered away from endfaces 74, 76 at an unstressed and unflexed condition. Seat ring secondsurfaces 132, 134 face reinforcing rings 100, 102 for bearing engagementand support against reinforcing ring first surfaces 112, 114. Seat ringthird surfaces or ball engaging surfaces 136, 138 generally face ballmember C for fluid sealing engagement with the ball. Flanges or lips140, 142 extend axially outward of seat ring first surfaces 128, 130 atouter peripheral surfaces 144, 146. These lips or flanges are preferablycontinuous about the seat rings and located so that their radial innersurfaces generally correspond to the outside diameter of conical discsprings 108, 110. Flanges or lips 140, 142 are bevelled at the radialoutermost areas thereof and are slightly rolled over the radial outeredges of the disc springs in the manner shown. While not necessary, thisarrangement advantageously maintains the seat rings and disc springstogether as a subassembly.

In the preferred arrangement of the invention, seat rings 104, 106 areconstructed from a resilient plastic material such aspolytetrafluoroethylene, polyethylene, or the like. It should be readilyappreciated, however, that other types of material such as acetyl resinsand the like could also be advantageously utilized. The particularmaterial chosen will, to some extent, be dependent upon the operatingconditions to which the valve will be subjected.

Frusto-conical disc springs 108, 110 include outer ends 152, 154 andinner ends 156, 158. The diameter at each outer end is such that a discspring may be received within the cylindrical cavity defined by theinner wall of the seat ring axial flanges 140, 142 and first surfaces128, 130. The inner diameter of each spring at ends 156, 158 issubstantially equal to the diameter of the opening 66, 68 through theassociated seat ring 104, 106.

The disc springs are selected so that their force is sufficient underpartial deflection to continuously urge the seat rings toward the ball.The springs must also allow stressing or compression thereof toward aflattened condition to accommodate ball shifting and engagement withseat ring third surfaces 136, 138. In the preferred embodiment hereunder discussion, seat ring first surfaces 128, 130 are configured so asto substantially fully stress disc springs 108, 110 at valve make-up,ie., move the disc springs from a frusto-conical shape toward asubstantially flattened configuration.

With reference to FIG. 4, the particular dimensional relationshipsbetween each seat assembly B and ball member C will be specificallydiscussed. Seat assemblies B will be discussed with particular referenceto the upstream seat assembly disposed at end fitting 14. It should beappreciated that the downstream seat assembly disposed at end fitting 16is identical thereto unless otherwise specifically noted. FIG. 4 is aschematic representation of seat assembly B and ball member C just priorto make-up at a preassembly reference position. In this referenceposition, disc spring 108 and seat ring 104 are relaxed and contact ismade between seat ring 104 and ball C at an annular contact line 160disposed at the radial innermost end of seat ring third or ball engagingsurface 136.

It is a particular feature of the invention that seat ring 104 engagesball member C at assembly such that a substantially uniform stressdistribution occurs along the entire extent of the seat ring thirdsurface 136. Since seat ring 104 is configured to exert a spring-likemechanical elasticity against the ball member C at assemblyindependently of disc springs 108, 110, the arcuate contour of ballengaging surface 136 must be configured to distort in a predictable andcontrolled manner for accomplishing the uniform stress distributionobjective. It has been found that in order to obtain this objective, theradius of curvature of surface 136 in an unstressed, unassembledcondition must be greater than the radius of curvature on the outer wallsurface of the ball member C. In addition, the seat ring 104 and discspring 108 are sized so that when assembled axially between valve bodyshoulder 70 and ball member C, the seat ring is flexed outwardly towardsassociated shoulder 70 and stressed to have a radius of curvature atsurface 136 generally equivalent to the radius of the ball member, thussealingly engaging the ball member over the entire extent of the surface136. The disc spring 108 is simultaneously stressed toward a flattenedcondition and, therefore, additionally acts to continuously urge seatring third surface 136 toward engagement with the ball member. Such auniformly stressed, full surface engagement will occur when the ballmember C and composite seat members B are sized so that at valveassembly from the preassembly reference position of FIG. 4, the seatring 104 and disc spring 108 are flexed and stressed to have an axialdisplacement at the area of seat assembly central opening 66 equal to anaxial spacing of a radial innermost end of seat ring second surface 132from the ball valve member C plus an axial displacement of the discspring 108 from shoulder end face 74 at an equicentric position to theaxial spacing.

In other words, and with continued reference to FIG. 4, seating surface136 contorts to match the spherical surface of the ball where dimensionk is equal to the sum of dimension l plus dimension j. Dimension krepresents the axial displacement of central opening 66 comprising adisplacement of disc spring inner end 156 toward the end face 74 ofshoulder 70. Dimension j represents the axial spacing of the radiallyinnermost end of seat ring second surface 132 from the ball member C.Dimension l represents the axial displacement of disc spring 108 fromend face 74 of shoulder 70 at an equicentric position to the radiallyinnermost end of seat ring second surface 132.

Recognizing this axial spacing or relationship, the relaxed seat ringspherical surface diameter D_(s) and the radial gap, dimension g,between ball member C and the seat ring at the radially innermost end ofsecond surface 132 may be calculated given certain readily determinabledimensions of the ball valve A. More specifically, the radial gap andthe relaxed seat ring spherical surface diameter D_(s) can be determinedusing known geometrical methods, given the seat ring 104 insidediameter, dimension d; the ball member diameter, dimension D; theoutside diameter of the seat ring ball engaging surface 136 or radiallyinnermost end of second surface 132, dimension N; the outside diameterof the disc spring 108, dimension E; and, the relaxed composite seattaper, dimension k, which is typically determined from the relaxation ofthe seat ring 104 and disc spring 108 necessary to compensate for theexpected seat wear. These dimensions are typically given parametersdetermined by the size of the valve which is desired and are determinedaccording to conventional industry design standards. There is a uniquespherical diameter D_(s) and a unique seat-to-ball radial gap g for eachseat ring 104, 106 corresponding to each set of given valve parameters,D, d, N, E, and k, such that when the seat ring 104, 106 is deformedupon assembly, the seat ring engaging surface 136, 138 conforms to thespherical surface of the ball member C.

In the preferred embodiment of the invention as shown in FIGS. 2 and 3,seat assemblies B are configured so that at the preassembly referenceposition, frusto-conical disc springs 108, 110 and seat rings 104, 106have their smaller diameter ends more closely spaced toward the ballmember. With reference to the upstream seat assembly of FIG. 2, theextent of the taper at the disc spring inner end 156 is predetermined tobe a dimensional amount corresponding to the expected wear on thedownstream seat ring 106 (FIG. 3) over the cycle life of the valve. Thefirst surface 128 of seat ring 104 tapers in matable association withdisc spring 108. The seat ring second surface 132 is disposed for closeabutting engagement to the first or bearing surface 112 of thereinforcing ring 100. As best illustrated in FIG. 4, and in thepreassembly reference position, the seat ring third or ball engagingsurface 136 is arcuately contoured to have a spherical surface diameterslightly greater than the ball member diameter and axially offsettherefrom. The radially innermost end of the engaging surface 136contacts the ball member C at an annular contact line 160 with a ballclearance gap thus being included at the radially outermost end of ballengaging surface 136.

Operation

Referring to FIGS. 5-10, description will hereinafter be made withreference to operation of the new ball valve and seat assembly. FIG. 5shows the valve in a fully assembled, valve open position (no load fluidpressure condition). In this position the two seat assemblies B havebeen shifted from the unstressed condition shown in FIGS. 2-4 to a fullystressed condition. Sizing of the ball member C, seat assemblies B andshoulders 70, 72 are such as to provide this relationship at ball valveassembly or make-up.

More particularly, and with particular reference to FIGS. 5-7, the seatassemblies are disposed at an assembled condition such that opposed seatrings 104, 106 are compacted between the associated reinforcing rings100, 102 and disc springs 108, 110 to compress the seat rings. The seatrings 104, 106 are further rotatably flexed at valve make-up away fromeach other and towards associated shoulders 70, 72 generally about theirouter peripheries and against disc springs 108, 110 in response toengagement between ball engaging surfaces 136, 138 and ball member C.This action compresses the associated disc springs 108, 110 toward asubstantially flattened condition. In the position of FIGS. 6 and 7, thedisc springs 108, 110 are preferably deflected through a travel distance(dimension k in FIG. 4) predetermined by the reasonable expectancy ofwear on the downstream seat ring 106 over the cycle lift of the valve A.

The combination flexure of the seat rings 104, 106 and the disc springs108, 110 provides a composite spring seat ring assembly which has fourprincipal advantages. The first is to provide a controlled preload ofthe seating surfaces against the ball. Since some loading is necessaryto maintain a seal, most prior art ball valves accomplish the preload bycrushing the seat rings between the ball and the flange or shoulder atassembly which, in effect, clamps the ball against movement. With seatrings constructed of harder plastic materials, this resulted in anunacceptably high operating torque. The controlled preload of thepresent invention, however, provides a seat surface against the ball inresponse to a flexing action rather than a crushing action and therebyoffers a reasonable operating torque. Second, the seat ring and discspring combinations operate to maintain a fluid seal at low seatpressures. Without spring loading of the seat rings against the ball,the seats are more likely to leak at low pressures, i.e., when pressureloading against the ball is less. Thirdly, a seal which compensates forseat wear and manufacturing tolerance is provided. As the seats wearduring valve operation, the seat composites relax against the ball,thereby extending the leak tight cycle life. Fourthly, the combinationflexure resists the problem of ball sag which may deform the seats bythe forces of ball member weight.

If the only spring action were provided by the disc springs with noadditional spring action being provided in the seat rings, the discsprings would have to overcome the elasticity of the seat rings in orderto flex them against the ball for wear compensation purposes.

Upon assembly, the disc spring and seat ring composite assemblies of thepresent invention are largely flattened and flexed away from the supportrings, i.e., seat ring second surfaces 132, 134 are flexed away fromportions of the reinforcing ring first surfaces 112, 114. Such actionprovides flexure reserve gaps 170, 172 to accommodate seat ring and discspring relaxation while simultaneously maintaining a preload againstball member C.

Five principal advantages are provided by reinforcing rings 100, 102 incombination with the disc springs and seat rings of the presentinvention.

The first is that they operate to reduce the seat stress on thedownstream seat ring 106. Without the rings 100, 102, pressure behindthe upstream seat ring 104 over an effective pressure area out tocounterbore step 78 imparts a load on the downstream seat ring 106 anddisc spring 110. With the inclusion of an upstream reinforcing ring 100,the effective pressure area of load translated to the downstream seatring is reduced by the additional surface area of reinforcing ring firstsurface 112 which supports and reinforces upstream seat ring 104 againstload pressures. The reduced load on the downstream seat ring 106 in avalve closed position provides reduced seating area stress and,consequently, reduced seat wear to extend the leak tight cycle life ofthe valve.

Secondly, the support ring 100 operates to support the upstream seat 104against caving in under pressure. In prior systems lacking the upstreamreinforcing ring 100, the upstream seat ring 104 can cave in under along duration static load. Thirdly, during cycling as the ball engagingsurface 136 partially spans the ball opening while maintaining ballsealing engagement, the upstream reinforcing ring 100 supports the seatring 104 to prevent a blowing-in bulge. An upstream cave-in or blow-inbulge of the seat ring 104 immediately upsets the sealability of thedownstream seat assembly.

Because of these aforementioned advantages the upstream reinforcing ring100 retains the seat ring 104 such that the allowable pressure on theseat ring can be increased over that allowable pressure which ispermissible when a reinforcing ring is not present.

Fourthly, the downstream support ring 102 also provides a positive stopagainst which the second surface 134 of seat ring 106 can form aflange-seat posterior seal. Most conventional seat ring materialsreadily crush upon assembly between the disc spring and the counterborestep or flange 80. Without the support ring 102, the seat 106 can tooreadily slip beyond this thin flange in the body of the valve.Particularly with hard plastics such as polyethylene, a more positivestop is necessary to effect a posterior seal.

An additional, fifth advantage of reinforcing rings 100, 102 resides inretarding back creep of the seat rings 104, 106 and particularly, thedownstream seat ring 106. The ball member C, at a valve closed positionwith a load acting against the upstream seat assembly and without adownstream support ring 102, more readily displaces the downstream seatring 106 toward the center of the valve body, especially if the seatmaterial is polytetrafluoroethylene or the like. Such displacement orcreep acts to relieve the seating surface preload necessary to maintainan effective seal.

It should be noted that even though the present invention encompasses afloating ball design, ball member C does not necessarily axially shiftor float toward the downstream seat assembly to effect a downstream seatseal in a valve closed and loaded condition. Since the downstream discspring 110 is substantially flattened against shoulder 72 at assembly,the downstream seat ring 106 is substantially contained on all foursides and the force against the ball engaging surface 138 is evenlydistributed over the entirety of that surface. The loading force doesnot distort seat ring 106 to allow an axial shift of ball member Cdownstream to effect a principal seal at the downstream seat ring.Rather, the invention encompasses a seat ring seal at both the upstreamand downstream seat assemblies throughout the life of the ball valve.However, even after excessive wear to the downstream seat ring may havecaused a break in the upstream seal, the subject ball valve will notfail as the downstream seat assembly will still effect a seal.

With reference ot FIGS. 8, 9 and 10, a ball valve A' which has undergoneconsiderable wear at the downstream seat assembly associated with endfitting 16' is illustrated in a valve closed position under elevatedfluid pressure conditions with the direction of fluid flow beingdesignated by the arrow adjacent the valve inlet. As is there shown,ball member C' is forced in response to fluid pressure to shift axiallytoward should 72 and against the downstream seat ring assembly such thatdisc spring 110' remains substantially flattened. Due to the substantialwear of seat ring 106', gap 172' is expanded accordingly. Ball engagingor third surface 138' of downstream seat ring 106' remains in sealingengagement with the surface of the ball member C' to provide afluid-tight seal with equal stress distribution across the extent ofsurface 138'.

The upstream seat assembly associated with end fitting 14' is flexedtoward the direction of movements of the ball member and is partiallyrelaxed from its initially assembled condition to accommodate the wearof downstream seat ring 106' while maintaining a fluid-tight seal withthe surface of the ball member C'. Disc spring 108' is relaxed from asubstantially flattened condition to the extent required to compensatefor the downstream seat ring wear. Upstream seat ring 104' has alsorelaxed to a similar extent to partially close flexure reserve gap 170'against the first surface 112' of the upstream reinforcing ring 100'.Because of the rotational flexing of seat ring 104', the seat ringsecond surface 132' is moved toward a contacting relationship with thefirst surface of reinforcing ring 100'. The ball engaging surface 136'of upstream seat ring 104' remains in substantial sealing engagementwith the surface of the ball member C'. The ball deforms a radiallyinnermost portion of surface 136' so that at least that portion has aspherical conformation in mating engagement with the ball member. Whenthe valve A' of FIG. 8 is placed in the valve open position, ball C'will shift axially back towards end fitting 14' such that equal pressurewill be exerted on the ball member by the disc springs 108', 110'.

The ball valve A with seat assemblies B described in detail hereinaboveis deemed to provide a substantial improvement over those arrangementspreviously known in the art. The subject design permits the seatassemblies to be flexible and deflect in a predictable and controlledmanner at initial assembly to facilitate compensation for seat wear,manufacturing tolerances and ball sag, and to provide a controlledpreload for improved ease of operation and low pressure sealing. Theball engaging surfaces of the seat ring assemblies are proportioned andconfigured for distorting to matable sealing engagement with the ballsurface at assembly for providing equal stress distribution across theentire extent of surfaces 136, 138. The inclusion of support rings 100,102 in combination with the improved seat rings 104, 106 and discsprings 108, 110 prevents the problems of blowing-in bulge, seatcave-in, high downstream seat stress and back creep and posteriorseat-to-shoulder leakage, and simultaneously does not inhibit theoperational advantage of the seat ring and disc spring combination.

Other modifications not specifically shown in the drawings may bereadily incorporated into seat ring assemblies B without in any waydeparting from the overall invention. It may, for example, be desirableto slightly modify the relative dimensional characteristics between theseat rings, reinforcing rings and disc springs to accommodate particularoperational requirements.

The invention has been described with reference to a preferredembodiment. Obviously, modifications and alterations will occur toothers upon a reading and understanding of this specification. It is ourintention to include all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalentsthereof.

Having thus described the invention, we now claim:
 1. A ball valvecomprising:a body having a central passageway; a ball member including afluid flow opening therethrough, said ball member being positioned insaid passageway and mounted for selective rotation between valve openand closed positions to control fluid flow through said valve, said ballmember further including a radius of curvature on an outer wall surface;a pair of radially inward extending shoulders in said passagewaydisposed circumferentially thereof on opposite sides of and generallyfacing said ball member; a pair of radially inward extending bearingsurfaces in said passageway disposed circumferentially thereof onopposite sides of said ball member, each of said bearing surfacesgenerally facing an associated one of said shoulders; and, a pair ofcomposite seat member assemblies positioned axially in said passagewayon opposite sides of said ball member between an associated shoulder andbearing surface for fluid-sealing engagement with said ball member, eachof said seat member assemblies comprising: a seat ring adapted forelastic flexure generally toward and away from the associated bearingsurface and including a central opening, a first surface generallyfacing the associated shoulder, a second surface abutting the associatedbearing surface, and a third surface facing said ball member for sealingengagement with said ball member outer wall surface, said seat ringthird surface being contoured and having a radius of curvature in anunstressed, unassembled condition greater than the radius of said ballmember; and, a disc spring having a central opening and a generallyfrusto-conical configuration in an unstressed condition interposedbetween said seat ring and the associated shoulder; said ball member andpair of composite seat member assemblies being sized so that whenassembled axially between said shoulders, each seat ring is flexted awayin a curved manner from the associated bearing surface and stressed tohave a radius of curvature at said seat ring third surface the same assaid ball member radius of curvature and is disposed in sealingengagement with said ball member over the extent of said seat ring thirdsurface with equal stress distribution across the seat ring thirdsurface, each disc spring being stressed to a flattened condition forcontinuously urging the third surface of the associated seat ring towardengagement with said ball member.
 2. The valve as defined in claim 1wherein said ball member and pair of composite seat member assembliesare sized so that when assembled from a preassembly reference position,the seat ring and disc spring of each assembly are flexed and stressedto have an axial displacement at said central openings thereof equal toan axial spacing of a radially innermost end of said seat ring secondsurface from said ball member plus an axial displacement of said discspring at an equicentric position to said axial spacing.
 3. The valve asdefined in claim 2 wherein said disc spring axial displacement at thecentral opening thereof comprises a displacement of said disc springtoward said associated one of said shoulders.
 4. The valve as defined inclaim 1 wherein said seat rings each include an axially extendingcircumferential flange at the first surface thereof for locating theassociated disc spring relative thereto.
 5. The valve as defined inclaim 1 wherein said ball member is axially movable in said passagewaywhen said valve is in said closed position to accommodate ball membershifting toward one of said shoulders in response to fluid pressure, theseat ring associated with the other of said shoulders being flexedtoward the direction of movement of said ball member in cooperation withthe influence of its associated disc spring in order that the thirdsurface thereof will be urged toward continuous contact with said ballmember.
 6. The valve as defined in claim 1 wherein each bearing surfaceis axially spaced from said ball member in said passageway to an extentwhich precludes abutment with said ball member and which inhibitsdistortion and displacement of the associated seat ring between thebearing surface and said ball member.